Achieving Safe Liberation During Weaning From VV-ECMO in Patients With Severe ARDS: The Role of Tidal Volume and Inspiratory Effort

Weaning from venovenous extracorporeal membrane oxygenation (VV-ECMO) has not been not well studied. VV-ECMO can be discontinued when patients tolerate noninjurious mechanical ventilation (MV) during a sweep gas-off trial (SGOT). However, predictors of safe liberation are unknown.

Can safe liberation from VV-ECMO be predicted at the bedside?

Two observational studies of adults weaned from VV-ECMO for severe ARDS at Toronto General Hospital were conducted. MV settings, respiratory mechanics, and clinical variables were analyzed to predict safe liberation from VV-ECMO, defined a priori as avoida7ce of ECMO recannulation, increased MV support, need for rescue therapy, or hemodynamic instability developed within 48 h following decannulation.

During both studies, 83 patients were weaned from VV-ECMO, 21 (25%) of whom did not meet the criteria for safe liberation. In the retrospective study, higher tidal volume per predicted body weight (OR, 1.58; 95% CI, 1.05-2.40; P = .03) and heart rate (OR, 1.07; 95% CI, 1.022-1.15; P = .01) at the end of SGOT were significantly associated with increased odds of unsafe liberation when adjusted for age (OR, 1.02; 95% CI, 0.95-1.09; P = .63) and sequential organ failure assessment score (OR, 1.16; 95% CI, 0.86-1.56; P = .34). Change in ventilatory ratio had an imprecise association (OR, 2.7; 95% CI, 0.94-7.95; P = .06) with unsafe liberation when adjusted for age (OR, 1.03; 95% CI, 0.96-1.10; P = .42), sequential organ failure assessment score (OR, 1.11; 95% CI, 0.81-1.51; P = .52), and heart rate (OR, 1.07; 95% CI, 1.01-1.13; P = .02). In the prospective study, patients who had unsafe liberation from VV-ECMO also had significantly higher inspiratory efforts (esophageal pressure swings, 9 [7-13] vs 18 [7-25] cm H₂O; P = .03) and worse outcomes (longer MV duration, ICU and hospital length of stay).

Patients with higher tidal volume, heart rate, ventilatory ratio, and esophageal pressures swings during SGOT were less likely to achieve safe liberation from VV-ECMO.